os_version and co should be os.version

[timeless@…]

​http://darwinports.opendarwin.org/docs/ch04s02.html

os_version

Version number of operating system (ie "6.0"). Read Only.

Error: Error executing darwin: can't read "os_version": no such variable

I tried writing a port based on this advice, it didn't work.

The following did work: variant darwin {

configure.args-append --host=${os.arch}-apple-rhapsody${os.version}

}

[landonf@…]

Fixes committed.